Peter Sandiford, Foundations of educational psychology nature’s gifts to man, New York, Longmans Green, (1938) 1940, p. 259.

A paramecium, for example, normally exhibits the back paddling, turning, and forging-ahead movements whenever it meets an obstacle. But, as Day and Bentley showed, a paramecium in a fine capillary tube partially filled with water will finally turn ove rand swim in the opposite direction in its efforts to escape. Yet no paramecium in its ordinary habitat ever turns a somersault.
Morgan’s dog finally hit upon the variant, grasping the stick by the end instead of the middle, which enabled it to drag it through tha palings of the fence. A caddis worm will construct a new tube if ejected from an old one and prevented from returning to it ; but not before it has made many attempts to return to the old one. Salmon ….